In human beings, the probability of getting a male or a female child is 50%. Explain with the help of a flow diagram only.
Generated by claude-sonnet-4-6 · 2026-06-15 06:45 · grounding rag
Model Answer
Flow Diagram:
$$\text{Father (44+XY)} \xrightarrow{\text{produces}} \begin{cases} 44+X \text{ (50%)} \\ 44+Y \text{ (50%)} \end{cases}$$
$$\text{Mother (44+XX)} \xrightarrow{\text{produces}} 44+X \text{ (100%)}$$
$$\downarrow$$
$$44+X + 44+X = 44+XX \Rightarrow \textbf{Girl (50\%)}$$
$$44+X + 44+Y = 44+XY \Rightarrow \textbf{Boy (50\%)}$$
Since the father produces two types of sperms (X and Y) in equal numbers, the probability of a male or female child is always 50%. The mother always contributes X chromosome.
Source: Chapter 7, Sexual Reproduction
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Explanation
- The key point examiners look for is that sex determination depends on the father's sperm, not the mother's egg (mother always gives X).
- Show clearly that X-sperm → girl, Y-sperm → boy, each with 50% chance.
- The flow diagram is mandatory as the question specifies it — no diagram means losing marks even if the concept is written correctly.
- Use correct chromosome notation (44 autosomes + sex chromosome).